High-power lasers, particularly excimer lasers, are used in continuous manufacturing processes, such as for micromachining, where the cost of operation is greatly influenced by the amount of downtime required to maintain the lasers. Although the lasers themselves and especially their components often account for only a small portion of the overall cost of the manufacturing machines in which they are used, any interruption in the operation of the lasers can suspend production along an entire fabrication line.
For example, high-power excimer lasers used in microlithographic fabricators of semiconductors or flat panel displays are typically operated on a 24-hour per day basis, i.e., without interruption except for scheduled or unscheduled maintenance. While the lasers are made to be highly reliable, high-power ultraviolet pulses produced within the lasers eventually degrade the optical components of the laser leading to an unacceptable loss of function or other failure of the lasers. Laser manufacturers can predict mean time between failures along with mean time to repair the lasers, and maintenance downtimes are often scheduled on this basis.
To simplify and speed the repair of the high-power lasers, the lasers are typically built in a modular form with one or more self-contained oscillator chambers in combination with a succession of self-contained optical module subsystems. The individual modules can be removed and replaced independently of the other modules on a schedule intended to extend the overall lifetimes of the lasers.
However, not all failures occur according to predictions, and emergency repairs during unscheduled downtimes are sometimes necessary. The modular form of the laser components speeds the repair, but diagnosing which component or combination of components is responsible for the failure can complicate and delay the necessary repair. For example, repair technicians may need to replace one module after another in a sequence until the failed module is discovered. Any such delay, particularly on an unscheduled basis, can be extremely costly.